Optimum sintering conditions for optical properties of translucent aluminum nitride ceramics

• 来源期刊: 科学通报（英文版）
• 年，卷（期）: 2009,（5）
• 页码范围: 842-845
• 页数: 4页
• 语种: 英文
• DOI: 10.1007/s11434-009-0115-5

摘要

High translucency is one of the excellent properties of AIN ceramics because of its wide optical band gap energy of 6.2 eV. We have achieved success in producing AIN ceramic tube of 98% total visible light transmittance at 0.6 mm thick tube wall by applying an improved sintering technique. This AIN ceramic was produced by sintering at 1880℃ using Ca3Al2O6 as a sintering additive and in reduction atmosphere to remove the sintering additive from the final sintered material. After the sintering, the annealing with Al2o3 was carried out to improve the transmittance of AIN ceramics. The amount of metal impurities and carbon were 27ppm and 100ppm, respectively. It is noteworthy that the amount of oxygen in AIN ceramics after the annealing was 0.36wt% which was higher than the 0.07wt% of the as-sintered AIN ceramics. Therefore, total transmittance was improved by the oxygen doping. On the other hand, thermal conductivity of AIN after the annealing was lowered by 35% compared with that of as-sintered AIN. Positron Annihilation Lifetime (PAL) measurement was applied to investigation of a relationship between the total transmittance and lattice defects. The present PAL results confirms the presence of negatively charged atomic-size vacancies that is aluminum site vacancies and also sug-gests the increase in the concentration of the vacancies after the annealing compared with that of the as-sintered material. However, it can be concluded that there is no relation between aluminum site va-cancies and the light transmittance of AIN ceramics.